SHOOT AND ROOT EVALUATIONS ON SEEDLINGS FROM Coffea GENOTYPES

SHOOT AND ROOT EVALUATIONS ON SEEDLINGS FROM Coffea GENOTYPES(¹)

LUIS CARLOS DA SILVA RAMOS(²,⁴) and ALCIDES CARVALHO(²,³)

ABSTRACT

Roots and shoots from seedlings of 29 coffee genotypes were studied to better characterize the entries from the Coffea germplasm bank of the Instituto Agronômico (IAC), Campinas, State of São Paulo, Brasil. The varieties were seeded in a randomized complete block design with 6 replications and 10 plants per plot. The characters evaluated were: plant (PL), shoot (SL) and root (RL) length; total plant (PDM), shoot (SDM), root (RDM) and lateral root (LRDM) dry matter. A lateral root index (LRI) and shoot root dry matter (SRDM = SDM/RDM) and length ratios; (SRL = SL/RL) were calculated. The dwarf varieties (Catuaí, Icatu-caturra, Vila Sarchi, San Ramon, Vila Lobos, São Bernardo) presented higher LRDM and lower SDM than the normal size varieties such as Mundo Novo, Bourbon Vermelho, Arábica, Amarelo de Botucatu, Glaucia, etc. The varieties Macrodiscus, Icatu-caturra, Bourbon Amarelo, Vila Lobos and C. congensis showed higher root development related to shoot. The Arábica coffee standard variety showed intermediary root and shoot development. Genotypes of high yield background were higher in SL and SDM, while the dwarf types had only lower SL than the normal ones, but higher RL and dry matters. Seedlings from genotypes of known higher field drought tolerance had lower SL and RL, but higher RDM. Significant phenotypic and genotypic correlation coefficients were obtained, such the genotypes for PL and PDM (r = 0.64; P = 0.01), SL and SDM (r = 0.40; P = 0.05), SDM and LRDM (r = 0.52; P = 0.05), RDM and LRI (r = 0.68; P = 0.01), LRI and SRDM (r = 0.85; P = 0.01) and LRI and LRDM (r = 0.84; P = 0.01). High genotypic correlations suggest that selection directed to one character will directly affect the other. Conversely, low or non-significant correlations suggest independence of association, an indication that it would be possible to select two characteristics to diverse directions. Selection could be done towards different goals to change root and shoot measures (length and dry matter) because they were genotypically independent. However, care should be taken in controlling the environmental effects, because of significant positive phenotypic correlations.

Index terms:Coffea, coffee, varieties, seedlings, shoots, roots.

RESUMO

AVALIAÇÕES NA RAIZ E NA PARTE AÉREA EM PLÂNTULAS DE GENÓTIPOS DE COFFEA

Efetuou-se um estudo comparativo do sistema radicular e da parte aérea em plântulas oriundas de 29 genótipos de Coffea do banco de germoplasma do Instituto Agronômico, em Campinas. Avaliaram-se as sementes dos genótipos aos 40 dias da germinação ocorrida em estufins de areia lavada. Verificou-se o comprimento total das plantas (PL), da parte aérea (SL) e das raízes (RL), a produção total de matéria seca das plantas (PDM), da parte aérea (SDM), das raízes (RDM) e das raízes laterais (LRDM). Com base nesses dados, calcularam-se relações entre parte aérea e raízes, tanto para comprimento (SRL = SL/RL) quanto para produção de matéria seca (SRDM = SDM/RDM), bem como o índice de raízes laterais (LRI). Observou-se que as variedades de porte baixo (Catuaí, Icatu-caturra, Vila Sarchi, San Ramon, Vila Lobos e São Bernardo) apresentaram maior LRDM e menor SDM do que as de porte normal (Mundo Novo, Bourbon Vermelho, Arábica, Amarelo de Botucatu, Glaucia, etc.). No contexto geral, as variedades Macrodiscus, Icatu-caturra, Bourbon Amarelo, Vila Lobos e C. congensis revelaram maior desenvolvimento do sistema radicular em relação à parte aérea. A variedade Arábica, tomada como padrão, mostrou desenvolvimento médio tanto no sistema radicular como na parte aérea. Genótipos cuja capacidade produtiva é classificada como alta apresentaram SL e SDM mais elevados, enquanto os tipos de porte reduzido tiveram apenas SL menor que os tipos normais, porém RL e matéria seca mais altos. Plântulas de genótipos considerados mais tolerantes à seca demonstraram menor SL e RL, no entanto maior RDM. Entre as correlações genotípicas e fenotípicas calculadas, algumas foram significativas, como as correlações genotípicas entre PL e PDM (r = 0,64; P = 0,01), SL e SDM (r = 0,40; P = 0,05), SDM e LRDM (r = 0,52; P = 0,05), RDM e LRI (r = 0,68; P = 0,01), LRI e SRDM (r = 0,85; P = 0,01) e LRI e LRDM (r = 0,84; P = 0,01). Altas correlações genotípicas sugerem que a seleção dirigida a um caráter irá afetar diretamente o outro, ao passo que correlações não significativas ou baixas sugerem independência de associação, indicando que seria possível selecionar, simultaneamente, duas características para direções diversas. Nesse caso, haveria possibilidade de alterar medidas de raiz ou parte aérea, haja vista a independência genotípica. Todavia, a indicação de correlações fenotípicas significativas sugere que se deva levar em conta os efeitos ambientes, na escolha do delineamento experimental adequado durante o processo de seleção.

Termos de indexação: Coffea, café, variedades, sistema radicular, parte aérea, plântulas.

1. INTRODUCTION

Coffee roots have been studied usually on adult or well developed plants regarding to how fertility, moisture and aeration affect root distribution in the soil (Franco & Inforzato, 1946), such better treatments of irrigation and fertilization can be defined (Guiscafré-Arrilaga & Gomez, 1942; Vaz, 1961; Inforzato & Reis, 1974).

Various characteristics related to root systems on seedlings and young plants have been studied with the purpose of characterizing varieties and species within the genus Coffea, such by Monaco et al. (1973), determining the root fresh matter; León & Umaña (1961), the main (apical) root length; Ramos (1980), the relative root surface; Ramos et al. (1978) and Ramos & Lima (1980), the shoot diameter, the root volume and the main root length.

Franco & Inforzato (1946) showed that the developmental pattern of coffee roots depends on the plant genotype. Shoot and seedling vigor also varied in different clones of C. canephora (Naidu et al., 1992). Plants with identical genotypes growing in a same soil presented the same root pattern. However, physical and chemical soil properties, or treatments, affect significantly root development, as noticed by Franco & Inforzato (1946). The shoot root ratio is raised by nitrogen fertilization in coffee seedlings (Bravo & Fernandez, 1964), for instance.

Ramos (1980) and Ramos et al. (1982) evaluating some coffee genotypes showed that the study of young plants germinating in homogeneous substrate is feasible, allowing a large number of plants to be studied simultaneously. Studying plants at seedling level could help in advancing selection, and early evaluations of morphological traits in plants may potentially select better plants at maturity.

Selection at seedling level for root growth vigor in hydroponic conditions will select for vigorous early growth of wheat in soil. Besides, vigorous shoot growth corresponded to vigorous root growth (Mian et al., 1993).

The objective of this work was to characterize roots and shoots of some Coffea genotypes from the local germplasm bank, at seedling stage. Attempts were additionally made to verify possible association of the measurements with field known features of the respective genotypes at adult stage, such productivity levels and drought tolerance backgrounds.

2. MATERIAL AND METHODS

Twenty seven varieties from Coffea arabica L. (normal size: Abramulosa ar1; Icatu; Bourbon Amarelo; Amarelo Botucatu; Angustifolia; Arábica; Anormalis; Bourbon Vermelho; Erecta; Abramulosa ar2; Volutifolia; Cioicie; Mundo Novo; Semierecta; Macrodiscus; Glaucia; Mucronata; Abissínica; Mokka LR; Dwarf size: Icatu Ct; São Bernardo; Catuaí Amarelo; Vila Sarchi; Vila Lobos; Catuaí Vermelho; Caturra Amarelo e San Ramon), one from C. canephora Pierre ex Frohener cv. Guarini, and one from C. congensis Frohener were studied.

Seeds from all genotypes were sown spaced 3 by 1 cm, in a 40 cm deep washed and sandy glass covered nursery. The experiment was assayed in a complete randomized block design with six replications and 10 samples per plot. Forty days after germination, or seventy seven days after seeding, ten samples were individually measured per treatment within blocks. The seedlings received regular irrigation and they developed on their own seed reserves, as no fertilizer was added.

The varieties were previously known under field conditions as of background plant sizes normal (ct) and caturra (Ct) type. The caturra type is a dwarf mutation which reduces internode length, thus reducing plant height (Krug et al., 1949). They were also known of background productivity levels, as high (H), medium (M) and low (L), and of drought tolerance levels, as high (H), moderate (M) and low (L). Information about drought tolerance levels were obtained from the local germplasm bank, where adult plants were yearly evaluated for yield and subjectively (visual grade points) for drought tolerance in years of scarce rain (unpublished evaluations provided by one author, A. Carvalho). There was no information on drought tolerance for the varieties Icatu Ct, Guarini and C. congensis, thus, they were excluded from analysis of variance when appropriate.

The following characteristics were measured: plant (PL), shoot (SL) and root (RL) length, taken from fresh seedlings; total plant (PDM), shoot (SDM), root (RDM) and lateral root dry matters (LRDM). Length and dry matter ratios between shoots and roots, and a lateral root index (LRI = LRDM*100/PDM) were also calculated. Dry matters were obtained after drying the fresh material at 75^oC for 48h.

For statistical analysis purpose, the genotypes were grouped in two classes, according to their known phenotypes at the adult age, that is, dwarf and normal sizes, in three classes according to their known adult background for yield potential and for drought tolerance, as before. Statistical analysis were done with SAS (1982) general linear models (GLM) because of unbalancing. Length data were analyzed with subsampling but dry matters, without; whereas mean tests were done according to the Duncan's multiple range test (DMRT). The genotype effect was analyzed as nested on the adult backgrounds when appropriate, and phenotypic and genotypic correlations were estimated, the second, as suggested by Kempthorne (1973).

3. RESULTS AND DISCUSSION

The analysis of variance of data from measurements on the 29 varieties, grouped by plant size, is shown in table 1. Significant effects were found for all the characteristics analyzed, except for PL, RL and SRDM in the dwarf group. In addition, variance values for RL and SL group sizes were significant, but not when combined in the total plant length, suggesting that variations in shoot and root length might not be close related. Significant seedling characteristics indicated that they were genotype dependent, or under genetic control. Previous works also indicated the genotypic effect in coffee seedling measurements (Vishveshwara & Raju, 1974; Naidu et al., 1992).

The block effect was highly significant and so was the interaction of blocks with treatments, but only available for PL, SL and RL (Table 2). Block interactions for plant length indicated that genotypes had different growth in different blocks.

When data were evaluated considering the phenotype backgrounds of productivity, drought tolerance and plant sizes (Table 3), SL, PDM, SDM and LRDM were significant for the first; PL, SL, SDM, RDM and LRDM were significant for the second, and SL, RL, RDM and LRDM for the third. Productivity is a characteristic highly related to the shoot tissues, as far as productive plants are more efficient in incorporating carbon in the leaves and branches, although the root genotype was shown to be limiting (Cardwell & Polson, 1972; Chloupek, 1978). Thus, it seems that the selection process for higher yield plants resulted in seedlings accumulating more dry matter in the shoots as compared to the roots, as indicated by a high SL and SDM (Table 4).

Root and shoot characteristics in coffee were associated with yield and environmental tolerances by Dublin (1968). Characteristics like SL, SDM, RDM and LRDM were significantly associated with the drought tolerance background, but not RL, LRI and PDM. Productivity and drought tolerance background interaction was significant for PDM and SDM (Table 3), an indication that yield and drought tolerance might be independent traits. Mazzafera & Carvalho (1987) indicated that yield and field drought tolerance were not associated in their coffee study. High yield genotypes which were not usually bred for suboptimal environmental conditions do not necessarily behave as drought tolerant (Fisher & Wood, 1979). Certain plants have fast growing root systems at seedling stage, as a way to avoid dry soil surfaces and to use subsurface water more efficiently (White & Castilho, 1992).

Normal size plants had only SL higher than dwarf plants, but lower root length and dry matters (Table 4). Significant differences were found comparing the mean values obtained for normal and dwarf plants, except for PL and LRI. The dwarf plants seemed to be more efficient as to shoot and root dry matter accumulation. However, it was not possible to separate individually normal from dwarf type plants at seedling stage by SL, since the range (minimum to maximum) was about the same for both groups (Table 5). Means of SL from the varieties Icatu Ct, Icatu ct, Mundo Novo and Catuaí confirmed this observation. Higher dry matter yields for dwarf coffee genotypes, in relation to normal ones, were also observed by Vishveshwara & Raju (1974).

No significant differences were found for the characteristics evaluated against the drought tolerance levels, except for SL and RDM. Seedlings from varieties with higher drought tolerance had lower SL and RL, but higher RDM (Table 4). In fact, only two dwarf varieties, named Catuaí Vermelho and Catuaí Amarelo, were previously known as drought tolerant and of high yield. These two varieties were bred from the original Caturra variety (Carvalho & Monaco, 1972).

The dwarf Caturra varieties were reported to be drought tolerant and with a large root system by Vishveshwara & Raju (1974). Mazzafera & Carvalho (1987) additionally classified the high yielding variety Catuaí Vermelho as drought tolerant, by field visual evaluation.

Genotypes of high yielding background had higher SL and SDM values. Ratios SRL and SRDM, although not statistically, were biologically superior for the high yield plants (Table 4). These obser- vations suggested that the high yielding group might be more efficient to accumulate dry matter in the aerial plant parts. However, seed yield is affected by the root genotype in soybeans (Cardwell & Polson, 1972) and the root system size was more important to yield and plant height in clover varieties (Chloupek, 1978). A large root system as compared to the shoot was associated with drought tolerance in some coffee species (Dublin, 1968).

The root surface area should be a more interesting characteristic to evaluate roots than RL (Ramos et al., 1980), and RDM better reflects root surfaces. Although the subjective evaluation of drought tolerance of adult trees were done under field conditions, and that adult plants might have other mechanisms of drought tolerance than seedlings (Levitt, 1980), a more developed root system should permit a better withstanding under drought conditions, as reported to other species (Hurd, 1974; Sullivan & Brum, 1975; Riveros et al., 1976; Torssell, 1976; Nour & Weibel, 1978).

Mean values of the characteristics from all varieties are in table 5. The varieties Macrodiscus, Icatu Ct and Bourbon Amarelo showed higher RDM. Macrodiscus showed one of the lowest SDM, and the highest LRI. Guarini and Abissínica showed lower RDM as well as lower LRI. Among the commercial varieties, Catuaí Amarelo and Vermelho showed very close values for all the characteristics evaluated, indicating genetic proximity. The Icatu ct variety showed higher values for all the characteristics evaluated, except for RL, while Mundo Novo showed lower values.

The higher values, related to those of Mundo Novo could be explained by the fact that Icatu originated from C. arabica and C. canephora hybridization, with backcrosses to C. arabica Mundo Novo (Monaco & Carvalho, 1975).

There were few genotype differences for PL and they were observed among the normal size plants (Table 5). Furthermore, only C. canephora cv. Guarini, C. congensis and Abramulosa ar1 showed significantly superior values of SL. The values for the RL means for those characteristics ranged from 9.3 cm for C. congensis and Guarini, to 12.2 cm for Vila Lobos, with intermediary values for other varieties of dwarf sizes, such San Ramon and Vila Sarchi. Perhaps a large root system at seedling stage would positively correlate at adult stage as it was reported in corn genotypes, where fast growing and high seedling root vigor tend to have massive root systems at maturity (Nass & Zuber, 1971). Observation on PDM data showed that some of the varieties had values even twice higher, as in the case of Mokka LR and Abissínica, with 0.57 and 0.56 g, respectively, compared to Icatu ct and Icatu Ct, with 1.04 and 1.05 g, respectively.

Genotypic and phenotypic correlations for all the evaluated characteristics are shown in table 6. Some of these characteristics showed high correlation because they are closely associated such as SDM and SL, or RDM and RL.

Phenotypic correlation between SL and RL was highly significant (r = 0.35; P = 0.01) while the genotypic was not (-0.26). Root and shoot dry matter correlations indicated that environment strongly affected both measures (r = 0.54; P = 0.01), but the genotype effects did not (-0.41). LRI genotypic correlations were highly significant with SDM, RDM, SRDM and LRDM. As expected, SDM and SRDM showed a highly genotypic correlation (r = 0.99; P = 0.01), as far they are related to each other.

Same observation was valid for RDM and LRDM. However, values of the genotypic correlation should be taken with reserve, as it was detected block interaction in length measures (Table 2).

High genotypic correlations suggest that selection directed to one character will directly affect the other. Conversely, low or non-significant correlations suggest independence of association, an indication that it would be possible to select two characteristics to diverse directions. For instance, selection can be done to change root and shoot measures (length and dry matter) towards different goals, because they were genotypically independent. However, care should be taken in controlling the environmental effects, which affected both root and shoot measures in same direction, as indicated by the significant positive phenotypic correlations.

ACKNOWLEDGMENTS

The authors wish to thank the researchers Oliveiro Guerreiro Filho, Maria Bernadete Silvarolla and Carlos Eduardo de Oliveira Camargo for reviewing the type-script.

⁽²) Seção de Genética, Instituto Agronômico (IAC), Caixa Postal 28, 13001-970 Campinas (SP), Brasil.

⁽³) In memoriam.

⁽⁴) With research grant from CNPq.

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⁽¹) Received for publication in january 18, 1996 and approved in march 11, 1997.

) Received for publication in january 18, 1996 and approved in march 11, 1997.

Publication Dates

• Publication in this collection
  16 June 1999
• Date of issue
  1997

History

• Received
  18 Jan 1996
• Accepted
  11 Mar 1997